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Background Conventional mechanical or alcohol-assisted photorefractive keratectomy (PRK) techniques for correction of hyperopia and hyperopic astigmatism were associated with inconsistent results. The aim of this study is to evaluate the 12-month visual and refractive outcomes of the relatively new single-step transepithelial photorefractive keratectomy (TE-PRK) for moderate hyperopia and hyperopic astigmatism. Methods This is a prospective interventional study. Forty-eight eyes of 30 patients with moderate hyperopia or hyperopic astigmatism with a cycloplegic spherical equivalent refraction (SEQ) between 2.0 and 4.5 diopters (D) underwent single-step StreamLight® TE-PRK using EX500 excimer laser (Alcon Laboratories, USA). The main outcome measures were recorded at 6 and 12 months postoperatively including assessment of logarithm of the minimum angle resolution (logMAR) uncorrected and corrected distance visual acuity (UDVA, CDVA), cycloplegic refraction, corneal topographic changes as well as post-PRK peripheral haze grading. Results The mean preoperative cycloplegic SEQ was significantly reduced from 3.21 ± 0.61 D to 0.35 ± 0.04 D and 0.41 ± 0.04 D at 6 and 12 months, respectively ( P  < 0.001). The mean preoperative UDVA significantly improved from 0.53 ± 0.02 logMAR to 0.07 ± 0.01 logMAR and 0.08 ± 0.01 logMAR at 6 and 12 months, respectively ( P  < 0.001) while the mean preoperative logMAR CDVA showed non-significant change over time throughout the study ( P  = 0.135). At the end of the study, 41 eyes (85.4%) achieved UDVA of 20/25 or better and no eye lost any lines of CDVA. Thirty-eight eyes (79.1%) had a postoperative cycloplegic cylinder of 0.5 D or less at 12 months. The mean preoperative mean keratometry showed significant increase at 6 and 12 months postoperatively ( P  < 0.001) while there was no significant change between the two postoperative visits denoting topographic stability ( P  = 0.058). The mean postoperative Q value at 6 and 12 months showed a significant prolate shift ( P  < 0.001). No haze was observed in 62.5% and 85.4% of the enrolled eyes at 6 and 12 months, respectively. Conclusions Single-step StreamLight® TE-PRK for moderate hyperopia and hyperopic astigmatism achieved acceptable visual and refractive outcomes. Trial registration : (Clinicaltrials.gov): NCT05261685, 2 March 2022, retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT05261685

To assess the safety, efficacy, and refractive predictability of half-fluence accelerated corneal collagen crosslinking (CXL) applied concurrently with photorefractive keratectomy (PRK), and compare the results to standard PRK. Refractive Services, The Eye Foundation, Coimbatore, India. Interventional comparative case series. Patients seeking refractive correction for myopia or myopic astigmatism were included in the study. Photorefractive keratectomy with concurrent half-fluence crosslinking (PRK Xtra) was performed in eyes with borderline suspicious tomography (not amounting to forme fruste keratoconus) or low pachymetry between 450 and 474 µm with an otherwise unremarkable corneal tomography. Eyes with normal corneal tomography and thickness between 475 and 500 µm underwent standard PRK. The minimum follow-up period was 1 year. In total, 109 eyes underwent PRK Xtra (Group A) and 118 eyes underwent PRK alone (Group B). The preoperative MRSE was -3.64 D and -3.38 D in Groups A and B, respectively ( =0.28). Group A had a significantly higher number of eyes with thinner corneas ( <0.01) and corneal tomographic abnormalities ( =0.02). At 1 year follow-up, 96.3% of eyes in group A as against 99.1% of eyes in group B achieved a best corrected distance visual acuity (CDVA) of 20/20 or better. No iatrogenic ectasia or hyperopic shift secondary to progressive flattening was noted in the PRK Xtra group. No significant difference in incidence of haze was noted. PRK Xtra showed comparable safety, efficacy, and stability to PRK in eyes with thinner pachymetry and tomographic abnormalities. Combining crosslinking with PRK in suspicious tomographies augurs for safe and predictable outcomes.

To identify the laser programming strategy that will achieve optimal refractive outcomes of LASIK with a topography-guided laser for eyes with a disparity between cylinder measured by manifest refraction and cylinder measured by topography. Six surgeons at 5 clinical sites in the USA. Retrospective data review. Preoperative, treatment, and postoperative data on 52 eyes that underwent topography-guided LASIK with the WaveLight EX500 Contoura Vision excimer laser ablation profile in which the vectors representing the preoperative refractive cylinder and the cylinder measured by the WaveLight Topolyzer™ VARIO Diagnostic Device (Vario cylinder) differed by >/= 0.50D and/or >/= 10 degrees of orientation were analyzed retrospectively. Data were contributed by six surgeons using the laser at 5 different clinical sites. Vector analysis of postoperative cylindrical refractive error and the actual laser programming strategy was used to calculate the cylindrical correction that would, theoretically, have completely eliminated postoperative refractive cylinder. This was compared to expected results using the preoperative manifest cylinder, the topographic cylinder, and the Phorcides Analytic Engine (Phorcides LLC, North Oaks MN; Phorcides). For analysis, subjects were stratified on the basis of the vector difference between Manifest and Topo cylinder (High, >0.75 D; and Low, ≤0.75 D). The poorest calculated theoretical outcomes were obtained with the manifest refraction (centroid: -0.43, 0.22; mean calculated error vector: 0.56 ± 0.42 D; p=ns). Better outcomes were obtained with the topographically measured refraction (centroid: 0.37, 0.02; mean calculated error vector: 0.47 ± 0.33 D; p=ns). The best outcomes were obtained with Phorcides (centroid: -0.15, 0.06; mean calculated error vector: 0.39 ± 0.28 D; p=ns). The mean error vector magnitude in the Phorcides Low group was significantly lower than for the Manifest and Topo Low groups (0.26 D vs 0.48 D and 0.33 D; p<0.01). The mean error magnitude in the Phorcides High group was nearly 0.25 D lower than for the Manifest High group (0.48 D vs 0.70 D; p<0.01), but was the same as for the Topo High group (0.48 D vs 0.48 D). Our study suggests that using the topographically measured cylinder or the cylinder selected by Phorcides will produce more desirable refractive outcomes than entry of the preoperative refractive cylinder as the basis for correction of myopia and myopic astigmatism with the WaveLight Contoura Vision excimer laser.

During fertilization, Pollen Receptor-Like Kinases (PRKs) control pollen tube growth through the pistil in response to extracellular signals, and regulate the actin cytoskeleton at the tube apex to drive tip growth. We investigated a novel link between membrane-integral PRKs and the actin cytoskeleton, mediated through interactions between PRKs and NET2A; a pollen-specific member of the NETWORKED superfamily of actin-binding proteins. We characterize NET2A as a novel actin-associated protein that localizes to punctae at the plasma membrane of the pollen tube shank, which are stably associated with cortical longitudinal actin cables. NET2A was demonstrated to interact specifically with PRK4 and PRK5 in Nicotiana benthamiana transient expression assays, and associated at discreet foci at the shank membrane of Arabidopsis pollen tubes. Our data indicate that NET2A is recruited to the plasma membrane by PRK4 and PRK5, and that PRK kinase activity is important in facilitating its interaction with NET2A. We conclude that NET2A–PRK interactions mediate discreet sites of stable interactions between the cortical longitudinal actin cables and plasma membrane in the shank region of growing pollen tubes, which we have termed Actin-Membrane Contact Sites (AMCSs). Interactions between PRKs and NET2A implicate a role for NET2A in signal transduction to the actin cytoskeleton during fertilization.

Although effective, a portion of photorefractive keratectomy (PRK) patients will suffer residual myopia or relapse to myopic regression. This retrospective, non-randomized, comparative study, aimed to compare the efficacy of primary PRK versus PRK performed as retreatment after previous surgery for myopia. Data regarding the right eye of 220 consecutive myopic patients undergoing repeat or primary PRK in 2013–2017 were extracted. Groups were matched for demographics and preoperative spherical equivalent, sphere, astigmatism, uncorrected and corrected distance visual acuity (UDVA and CDVA). Primary outcomes were an efficacy index (ratio between the postoperative UDVA and the preoperative CDVA), a safety index (ratio between the postoperative and the preoperative CDVA), postoperative UDVA and CDVA, and deviation from target refraction. Primary PRK showed significant superiority in logMAR UDVA (0.01 ± 0.05 versus 0.05 ± 0.10, p = 0.001), logMAR CDVA (0.01 ± 0.05 versus 0.04 ± 0.08, p = 0.01), efficacy index (1.00 ± 0.05 versus 0.97 ± 0.09, p = 0.003) and safety index (1.00 ± 0.06 versus 0.98 ± 0.08, p = 0.04) compared to repeat PRK, but had a significantly higher share of patients with postoperative spherical equivalent (74.5% versus 67.3%) and cylinder (74.5% versus 68.2%) in the range of ±0.5 D. To conclude, enhancement PRK leads to inferior efficacy and safety with greater deviation from target refraction. Adjusted nomograms for repeat PRK may be warranted.

Dry eye disease is the most common complication and a frequent cause of patient dissatisfaction after corneal laser refractive surgery, which includes laser-assisted in situ keratomileusis (LASIK), small-incision lenticule extraction (SMILE), and photorefractive keratectomy (PRK). It has a complex, multifactorial etiology and is characterized by a highly variable clinical presentation. A detailed preoperative screening and optimization of the ocular surface prior to refractive surgery are the key to minimizing the incidence and severity of postoperative dry eye. Diagnosis of postrefractive surgery dry eye remains a challenge as no single symptom or clinical parameter is confirmative of the condition, and the symptoms and signs may not correlate well in many cases. A thorough understanding of the pathomechanism of the disease and its manifestations is essential to facilitate a treatment approach that is individualized for each patient. This article reviews various aspects of postrefractive surgery dry eye including its epidemiology, etiopathogenesis, risk factors, diagnosis, and management.

To compare clinical outcomes between mechanical debridement photorefractive keratectomy (m-PRK) and trans-epithelial photorefractive keratectomy (t-PRK) in myopic patients. Eighty eyes of 40 myopic patients with age between 18 and 55 years were included in this study. In each patient, one eye was randomly assigned for t-PRK, using the Amaris laser's ORK-CAM software and the other eye for m-PRK, using a spatula. Stromal ablation was done by Schwind Amaris 750S. Uncorrected and best corrected visual acuity (BCVA), refractive outcomes, epithelial healing, pain, and discomfort were compared between the groups on day 1, 3, 7 and month 1, 3, and 6. Preoperative spherical equivalent (SE) were −3.97 ± 2.08 diopter (D) and −3.98 ± 2.06 D in m-PRK and t-PRK eyes, respectively (P = 0.981). Operation time was significantly shorter in the t-PRK group than m-PRK (P < 0.001). Postoperative pain was experienced significantly higher in the t-PRK group measured by 11-point numeric scale of pain questionnaire on the first postoperative day (P < 0.001). Photophobia, tearing, and vision fluctuation were also significantly higher in the t-PRK group postoperatively. However epithelial defect size and re-epithelialization time were lower in the t-PRK group (P = 0.012 and P < 0.001, respectively). Postoperative parameters including SE, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and contrast acuity did not show any significant difference between the two groups during all intervals. Although epithelial defect size and epithelial healing time were lower in t-PRK, postoperative pain, photophobia, and vision fluctuation were significantly less in the m-PRK group in the first postoperative days. There was no statistically significant difference between the groups after one week, and both mechanical and trans-epithelial techniques were shown to be safe and effective.

Background This review aims to explain the reasons why intraocular lens (IOL) power calculation is challenging in eyes with previous corneal refractive surgery and what solutions are currently available to obtain more accurate results. Review After IOL implantation in eyes with previous LASIK, PRK or RK, a refractive surprise can occur because i) the altered ratio between the anterior and posterior corneal surface makes the keratometric index invalid; ii) the corneal curvature radius is measured out of the optical zone; and iii) the effective lens position is erroneously predicted if such a prediction is based on the post-refractive surgery corneal curvature. Different methods are currently available to obtain the best refractive outcomes in these eyes, even when the perioperative data (i.e. preoperative corneal power and surgically induced refractive change) are not known. In this review, we describe the most accurate methods based on our clinical studies. Conclusions IOL power calculation after myopic corneal refractive surgery can be calculated with a variety of methods that lead to relatively accurate outcomes, with 60 to 70% of eyes showing a prediction error within 0.50 diopters.

To compare the intraocular pressure (IOP) obtained by Goldmann applanation tonometer (GAT), correcting applanation tonometer surface (CATS) and biomechanically corrected IOP (bIOP) of Corvis ST tonometer (CVS); and to determine the effects of manifest refraction spherical equivalent (MRSE), central corneal thickness (CCT) and mean corneal curvature (Km) on the IOP measurements of corneal refractive patients. This was a single-center, retrospective, cross-sectional study of 120 eyes of 64 patients from May 1, 2020 to June 1, 2021 who underwent laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). The level of agreement between the three tonometers was evaluated, and correlation between parameters was calculated using Pearson correlation. Mean preoperative to postoperative IOP in LASIK and PRK was 15.1 ± 3 to 11.3 ± 2.1 and 14.4 ± 2.6 to 12.1 ± 3 using GAT, 16.4 ± 2.8 to 13.1 ± 2.3 and 15.9 ± 2.6 to 13.7 ± 3 using CATS and 14.8 ± 2.4 to 12.9 ± 1.5 and 14.2 ± 2.4 to 12.6 ± 1.9 using CVS-bIOP. Preoperative IOP correlation between each tonometer pair showed that the lowest mean difference was between GAT and CVS-bIOP (0.32 in LASIK, 0.15 in PRK). Preoperative to postoperative IOP correlation of each tonometer resulted in a difference of 3.77, 2.30 in GAT; 3.32, 2.28 in CATS and 1.88, 1.62 in CVS-bIOP in the LASIK and PRK groups, respectively. Percentage change in CCT and Km was not correlated while change in MRSE had a weak relationship with percentage change in CVS-bIOP. Preoperatively, GAT and CVS-bIOP had the best agreement in IOP measurements. CATS recorded the highest IOP preoperatively and postoperatively. IOP decreased in the three tonometers after LASIK and PRK with GAT having the largest decrease. CVS-bIOP had the lowest change between preoperative and postoperative IOP measurements. Only percentage change in MRSE was correlated with percentage change in CVS-bIOP in the LASIK group.

PurposeTo investigate the differences in surgical results and the objective and subjective quality of vision (QoV) of patients after small incision lenticule extraction (SMILE) versus alcohol-assisted photorefractive keratectomy (PRK).MethodsMedical records of patients treated with SMILE and PRK were retrospectively examined. Visual quality, biometric parameters, Strehl ratio (SR), and corneal higher-order aberrations (HOAs) within a 6.0 mm area were recorded. The effective optical zone (EOZ) and decentration were measured using a tangential pre-post operation difference map. Subjective QoV and operation satisfaction were evaluated 6 months postoperatively using the Quality of Vision questionnaire.ResultsThe study comprised 100 eyes treated with SMILE (preoperative mean spherical equivalent (SE), − 4.52 ± 0.81 dioptres (D)) and 69 eyes with PRK (mean SE, − 4.21 ± 1.25 D). Six months postoperatively, the EOZ reduction was significantly larger in the PRK group (P < 0.001). Decentrations were comparable between the groups. Regarding visual symptoms, monocular diplopia was more common following PRK (P = 0.02), and 98 (98.00%) SMILE-treated and 67 (97.10%) PRK-treated patients were satisfied with the QoV. Both groups demonstrated significant increases in total HOAs, coma, and spherical aberration (SA) at 6 months postoperatively compared to preoperatively (P < 0.001); these values were significantly higher in the PRK (P < 0.05) compared to the SMILE group. SR increased significantly only in the PRK group (P < 0.05).ConclusionAlthough EOZ was more consistent with anticipated treatment and HOAs were fewer in SMILE, high patient-reported satisfaction and good corneal optical quality were achieved in both groups, indicating that both SMILE and alcohol-assisted PRK are excellent options for mild to moderate myopia correction.